TFT active matrix liquid crystal display devices with two layer gate lines, the first being the same level and material as gate electrodes

Abstract

There are disclosed various types of TFT active matrix liquid crystal display devices in which a pixel is divided into three parts, a capacitor is added to each pixel, light shielding is applied to each TFT, and the matrix is driven by a DC cancelling technique.

What is claimed is: 
     
       1. A liquid crystal display device having a plurality of pixels, each of said plurality of pixels including a thin film transistor, a pixel electrode and a holding capacitance element and disposed in each of intersecting regions defined by two adjacent scanning signal lines and by two adjacent image signal lines, wherein: each said thin film transistor comprises a gate electrode electrically connected to one of said two adjacent scanning signal lines associated therewith, a gate insulating film disposed on said gate electrode, a semiconductor layer disposed on said gate insulating film, and a source electrode and a drain electrode electrically connected to said semiconductor layer, respectively,   one of said source electrode and drain electrode of each said thin film transistor is electrically connected to said pixel electrode associated therewith, the other of said source electrode and drain electrode of each said thin film transistor being electrically connected to one of said two adjacent image signal lines associated therewith,   said scanning signal lines include a first conductive film and a second conductive film superposing with each other,   said holding capacitance element of each pixel comprises a first electrode electrically connected to said pixel electrode, a second electrode electrically connected to the other of said two adjacent scanning signal lines associated therewith, and a dielectric film interposed therebetween, and   said second electrode and said gate electrode are formed from a same conductive layer only, which conductive layer is a same level layer as that of said first conductive film of said scanning signal lines.   
     
     
       2. A liquid crystal display device according to claim 1, wherein said second conductive film has a smaller width than that of said first conductive film at least in crossover portions of said scanning signal lines and said image signal lines. 
     
     
       3. A liquid crystal display device according to claim 2, wherein each said gate electrode is directly connected to said first conductive film and is disposed in a non-overlapped relationship with said second conductive film of said one of said two adjacent scanning signal lines associated therewith. 
     
     
       4. A liquid crystal display device according to claim 2, wherein said second electrode of each said holding capacitance element is disposed in a non-overlapped relationship with said second conductive film of said other of said two adjacent scanning signal lines associated therewith. 
     
     
       5. A liquid crystal display device according to claim 2, wherein said first conductive film consists of a chromium film layer and said second conductive film consists of an aluminum film layer. 
     
     
       6. A liquid crystal display device according to claim 1, wherein each said gate electrode is directly connected to said first conductive film and is disposed in a non-overlapped relationship with said second conductive film of said one of said two adjacent scanning signal lines associated therewith. 
     
     
       7. A liquid crystal display device according to claim 6, wherein said second electrode of each said holding capacitance element is disposed in a non-overlapped relationship with said second conductive film of said other of said two adjacent scanning signal lines associated therewith. 
     
     
       8. A liquid crystal display device according to claim 1, wherein said second electrode of each said holding capacitance element is disposed in a non-overlapped relationship with said second conductive film of said other of said two adjacent scanning signal lines associated therewith. 
     
     
       9. A liquid crystal display device according to claim 1, wherein each said gate electrode is directly connected to said first conductive film and is left uncovered by said second conductive film of said one of said two adjacent scanning signal lines associated therewith. 
     
     
       10. A liquid crystal display device according to claim 9, wherein said second electrode of each said holding capacitance element is left uncovered by said second conductive film of said other of said two adjacent scanning signal lines associated therewith. 
     
     
       11. A liquid crystal display device according to claim 1, wherein said second electrode of each said holding capacitance element is left uncovered by said second conductive film of said other of said two adjacent scanning signal lines associated therewith. 
     
     
       12. A liquid crystal display device according to claim 1, wherein each said gate electrode is formed from a part of said first conductive film which is left uncovered by said second conductive film of said one of said two adjacent scanning signal lines associated therewith and which is extended as a branched portion in an orthogonal direction from the direction of said scanning signal lines, which orthogonal direction is substantially parallel to the direction of said image signal lines. 
     
     
       13. A liquid crystal display device according to claim 12, wherein said second electrode of said holding capacitance element of each pixel is formed from a part of said first conductive film which is left uncovered by said second conductive film of said other of said two adjacent scanning signal lines associated therewith and which is extended as a branched portion in a direction parallel but opposite the direction of the uncovered part of said first conductive film of said one scanning line which forms the gate electrode of said thin film transistor of that pixel. 
     
     
       14. A liquid crystal display device according to claim 13, wherein said second conductive film has a smaller width than that of said first conductive film at least in crossover portions of said scanning signal lines and said image signal lines. 
     
     
       15. A liquid crystal display device according to claim 14, wherein said first conductive film consists of a chromium film layer and said second conductive film consists of an aluminum film layer. 
     
     
       16. A liquid crystal display device according to claim 13, wherein said first and second conductive films constituting each of said scanning signal lines are dimensioned such that said second conductive film has a smaller width than said first conductive film. 
     
     
       17. A liquid crystal display device according to claim 16, wherein said first conductive film consists of a chromium film layer and said second conductive film consists of an aluminum film layer. 
     
     
       18. A liquid crystal display device according to claim 12, wherein said second conductive film has a smaller width than that of said first conductive film at least in crossover portions of said scanning signal lines and said image signal lines. 
     
     
       19. A liquid Crystal display device according to claim 12, wherein said first and second conductive films constituting each of said scanning signal lines are dimensioned such that said second conductive film has a smaller width than said first conductive film. 
     
     
       20. A liquid crystal display device according to claim 1, wherein said first and second conductive films constituting each of said scanning signal lines are dimensioned such that said second conductive film has a smaller width than said first conductive film. 
     
     
       21. A liquid crystal display device according to claim 1, wherein said plurality of pixels are arranged, on a substrate surface, together with a plurality of scanning signal lines and a plurality of image signal lines to form a matrix array having rows and rows of pixels in which each pixel is disposed in each of intersecting regions on said substrate surface defined by a pair of adjacent scanning signal lines and by a pair of adjacent image signal lines, said pair of scanning signal lines, respectively, being associated with adjacent pixels in a column direction and said pair of image signal lines, respectively, being associated with adjacent pixels in a row direction of said matrix array. 
     
     
       22. A liquid crystal display device according to claim 21, wherein each said gate electrode is formed from a part of said first conductive film which is left uncovered by said second conductive film of said one of said two adjacent scanning signal lines associated therewith and which is extended as a branched portion of that scanning line in the row direction. 
     
     
       23. A liquid crystal display device according to claim 22, wherein said second electrode of said holding capacitance element of each pixel is formed from a part of said first conductive film which is left uncovered by said second conductive film of said other of said two adjacent scanning signal lines associated therewith and which is extended as a branched portion in the column direction but opposite that of the uncovered part of said first conductive film of said one scanning signal line which forms the gate electrode of said thin film transistor of that pixel. 
     
     
       24. A liquid crystal display device according to claim 23, wherein said second conductive film has a smaller width than that of said first conductive film at least in crossover portions of said scanning signal lines and said image signal lines. 
     
     
       25. A liquid crystal display device according to claim 23, wherein said first and second conductive films constituting each of said scanning signal lines are dimensioned such that said second conductive film has a smaller width than said first conductive film. 
     
     
       26. A liquid crystal display device according to claim 25, wherein said first conductive film consists of a chromium film layer and said second conductive film consists of an aluminum film layer. 
     
     
       27. A liquid crystal display device according to claim 22, wherein said second conductive film has a smaller width than that of said first conductive film at least in crossover portions of said scanning signal lines and said image signal lines. 
     
     
       28. A liquid crystal display device according to claim 22, wherein said first and second conductive films constituting each of said scanning signal lines are dimensioned such that said second conductive film has a smaller width than said first conductive film. 
     
     
       29. A liquid crystal display device according to claim 28, wherein said first conductive film consists of a chromium film layer and said second conductive film consists of an aluminum film layer. 
     
     
       30. A liquid crystal display device according to claim 21, wherein said second electrode of said holding capacitance element and said gate electrode of said thin film transistor in each of said pixels are formed from a same conductive layer as that used for forming said first conductive film of said scanning lines. 
     
     
       31. A liquid crystal display device according to claim 21, wherein said second electrode of said holding capacitance element and said gate electrode of said thin film transistor in each of said pixels are formed from branched portions of said one and said other of said two adjacent scanning signal lines associated therewith, respectively. 
     
     
       32. A liquid crystal display device according to claim 1, wherein said second electrode of said holding capacitance element and said gate electrode of said thin film transistor in each of said pixels are formed from a same conductive layer as that used for forming said first conductive film of said scanning lines. 
     
     
       33. A liquid crystal display device according to claim 32, wherein said second conductive film has a smaller width than that of said first conductive film at least in crossover portions of said scanning signal lines and said image signal lines. 
     
     
       34. A liquid crystal display device according to claim 33, wherein said first conductive film consists of a chromium film layer and said second conductive film consists of an aluminum film layer. 
     
     
       35. A liquid crystal display device according to claim 32, wherein said first and second conductive films constituting each of said scanning signal lines are dimensioned such that said second conductive film has a smaller width than said first conductive film. 
     
     
       36. A liquid crystal display device according to claim 35, wherein said first conductive film consists of a chromium film layer and said second conductive film consists of an aluminum film layer. 
     
     
       37. A liquid crystal display device according to claim 1, wherein said second electrode of said holding capacitance element and said gate electrode of said thin film transistor in each of said pixels are formed from branched portions of said one and said other of said two adjacent scanning signal lines associated therewith, respectively. 
     
     
       38. A liquid crystal display device according to claim 37, wherein said second conductive film has a smaller width than that of said first conductive film at least in crossover portions of said scanning signal lines and said image signal lines. 
     
     
       39. A liquid crystal display device according to claim 38, wherein said first conductive film consists of a chromium film layer and said second conductive film consists of an aluminum film layer. 
     
     
       40. A liquid crystal display device according to claim 37, wherein said first and second conductive films constituting each of said scanning signal lines are dimensioned such that said second conductive film has a smaller width than said first conductive film. 
     
     
       41. A liquid crystal display device according to claim 40, wherein said first conductive film consists of a chromium film layer and said second conductive film consists of an aluminum film layer.